As a process for manufacturing m-phenylene type PGI.sub.2 derivatives which have an .alpha.-side chain containing 4 carbon atoms, processes shown in Charts 1 and 2 (disclosed in Japanese Laid Open Patent Application (Kokai) Nos. 36477/81 and 124778/83, respectively) and shown in the literature ("Advances in Prostaglandin, Thromboxane and Leukotriene Research", vol.15, p.279) are known. ##STR3##
However, the conventional manufacturing processes described above have a variety of drawbacks which are disadvantageous in the industrial production in large scale, i.e., in that the reproducibility is poor, a large number of steps need to employ column chromatography, the stereoselectivity and the regiospecificity are poor, reactions which are carried out at low temperature are necessary, operation is troublesome, yield is low and so on.